SGER: A Difference Frequency Generation Microscope

化学部的分析和表面化学计划将通过探索性研究（SGER）的小额赠款支持俄亥俄州州立大学的石楠艾伦教授的研究计划。这项工作的目标是开发一种新的方法，能够使用振动二阶光谱成像液体表面。虽然红外和拉曼显微镜是很好地利用固体表面上的成像膜的工具，使用振动差频（或和频）显微镜的非线性技术提供了显着更高的灵敏度成像的空气-液体界面。目前，和频光谱学用于从液体表面获得光谱;然而，和频成像远未普及，主要是因为技术复杂性。 艾伦教授和她的学生将利用红外显微镜技术设计一个差频显微镜的光学平台。 在这项高风险、高影响研究中要检验的假设是，将高重复率红色激光与连续波红外光源结合起来，将产生少量差频光子，通过仔细优化探测变量，可以对这些光子进行成像。或者，利用与红色激光脉冲相结合的高重复率红外源将提供大量光子，这些光子可以更容易地使用红外显微镜平台成像。这种具有分子选择性和高灵敏度的差频显微镜将应用于生物学、材料、环境和大气气溶胶研究中的成像。

The Analytical and Surface Chemistry program in the Division of Chemistry will support the research program of Prof. Heather Allen of Ohio State University through a small grant for exploratory research (SGER). The goal of this work is to develop a new method with the capability to image liquid surfaces using vibrational second-order spectroscopy. While infrared and Raman microscopy are well utilized tools for imaging films on solid surfaces, nonlinear techniques using vibrational difference-frequency (or sum-frequency) microscopy provides markedly greater sensitivity for imaging the air-liquid interface. Currently, sum frequency spectroscopy is used to obtain spectra from liquid surfaces; however, sum-frequency imaging is far from being commonplace mainly because of technical complexity. Prof. Allen and her students will utilize infrared microscope technology an optical platform for the design of a difference-frequency microscope. The hypothesis to be tested in this high risk high impact study is that combining a high repetition rate red laser with a continuous wave infrared source, will generate a small number of difference-frequency photons that could be imaged with careful optimization of detection variables. Alternatively, utilizing a high repetition rate infrared source combined with red laser pulses will provide a large number of photons that can more easily be imaged using the infrared microscope platform. This molecularly selective and highly sensitive difference-frequency microscope will have application to imaging in biology, materials, and environmental and atmospheric aerosol research.